Eran Grinvald

Single-beam coherent Raman spectroscopy and microscopy via spectral notch shaping

We present a simple and easily implementable scheme for multiplexed Coherent Anti-Stokes Raman Scattering (CARS) spectroscopy and microscopy using a single femtosecond pulse, shaped with a narrow spectral notch. We show that a tunable spectral notch, shaped by a resonant photonic crystal slab, can serve as a narrowband, optimally time-delayed probe, resolving a broad vibrational spectrum with high spectral resolution in a single-shot measurement. Our single-source, single-beam scheme allows the simple transformation of any multiphoton microscope with adequate bandwidth into a nearly alignment-free CARS microscope.

Self-Assembled Organic Nanocrystals with Strong Nonlinear Optical Response

Facile molecular self-assembly affords a new family of organic nanocrystals that, unintuitively, exhibit a significant nonlinear optical response (second harmonic generation, SHG) despite the relatively small molecular dipole moment of the constituent molecules. The nanocrystals are self-assembled in aqueous media from simple monosubstituted perylenediimide (PDI) molecular building blocks. Control over the crystal dimensions can be achieved via modification of the assembly conditions. The combination of a simple fabrication process with the ability to generate soluble SHG nanocrystals with tunable sizes may open new avenues in the area of organic SHG materials.

Enhanced Third-Harmonic Generation from a Metal/Semiconductor Core/Shell Hybrid Nanostructure

Nonlinear optical processes can be dramatically enhanced via the use of localized surface plasmon modes in metal nanoparticles. Here we show how more elaborate structures, based on shape-controlled Au/Cu2O core/shell nanostructures, enable further enhancement of the nanoparticle third-harmonic scattering cross-section. The semiconducting component takes a twofold role in this structure, both providing a knob to tune the resonant frequency of the gold plasmon and providing resonant enhancement by virtue of its excitonic states. The advantages and deficiencies of using such core/shell metal/semiconductor structures are discussed.

Real-time measurement of space-variant polarizations

A configuration for real-time measurement of unique, space-variant, polarizations is presented. The experimental results reveal that the full state of polarization at each location within the beam can be accurately obtained every 10 msec, limited only by the camera frame rate. We also present a more compact configuration which can be modified to determine the real-time wavelength variant polarization measurements.

Nonlinear immunofluorescent assay for androgenic hormones based on resonant structures

We report for the first time the use of two photon fluorescence as detection method of affinity binding reactions. We use a resonant grating waveguide structure as platform enhancement for detecting the interaction between fluorescent labeled Boldenone, a non-natural androgenic hormone, and a specific anti-anabolic antibody. We were able to detect a surface coverage of approximately 0.7 ng/mm(2).

Role of photonic bandgaps in polarization-independent grating waveguide structures

Polarization independence in a one-dimensional resonant grating waveguide structure involves the simultaneous excitation of two guided modes propagating in different directions. Possible simultaneous excitations occur when the two excited guided modes have either the same polarization, i.e., TE-TE (transverse electric) or TM-TM (transverse magnetic), or different polarizations, i.e., TE-TM. Simultaneous excitations may result in bandgaps and singularities. We confirm and show that in order to achieve polarization independence, it is necessary to find the conditions that minimize the effects of such bandgaps and singularities and experimentally demonstrate tunable polarization independence for simultaneously excited TE-TM-guided modes.

Analysis of light scattering off photonic crystal slabs in terms of Feshbach resonances

Techniques to deal with Feshbach resonances are applied to describe resonant light scattering off one dimensional photonic crystal slabs. Accurate expressions for scattering amplitudes, free of any fitting parameter, are obtained for isolated as well as overlapping resonances. They relate the resonance properties to the properties of the optical structure and of the incident light. For the most common case of a piecewise constant dielectric function, the calculations can be carried out essentially analytically. After establishing the accuracy of this approach we demonstrate its potential in the analysis of the reflection coefficients for the diverse shapes of overlapping, interacting resonances.

Real time achromatic measurement of space-variant polarizations

A compact configuration for real-time achromatic measurements of space-variant light polarization is presented. The experimental results reveal that the full state of polarization at each location within a light beam or at each wavelength can be obtained with accuracy of over π/18.

Cladding Amplification of Very Large Area Modes in a Novel Double-Clad Fiber

We propose and investigate theoretically a new concept for single mode amplification in active double-clad fibers. We show that the guided fundamental mode field diameter can reach 80 μm with good modal discrimination.

Single-Pulse CARS Spectroscopy Using a Resonant Photonic Crystal Slab Filter (RPCS)

We present a simple scheme for performing single-beam vibrational spectroscopy with a single femtosecond pulse without a pulse-shaper. High-resolution microspectroscopy and vibrational imaging is demonstrated using a narrowband probe defined by an RPCS filter.